Transmitting pressure in a hydraulic system

ABSTRACT

The transmission of pressure in a closed hydraulic system is accomplished by using an effective amount of benzylated and/or styrenated triaryl phosphate.

O iJnited States Patent 1 3,674,698

Weil July 4, 1972 [54] TRANSMITTING PRESSURE IN A 2,995,519 8/1961 Shatynski et a1 ..252/78 HYDRAULIC SYSTEM 3,352,780 11/1967 Groslambert ..252 33 3 I 3,384,686 5/1968 Boschan et a1 ..260/966 [72] inventor: Edward D. Well, Hastmgs-on-Hudson, 3,428.71, 2/1969 Sconce et a1 H 260/966 3,432,437 3/1969 Nail ..252/78 173| Assignec: Stauller Chemical Company, New York, 3,436,441 4/1969 Thompson ..260/966 NY, 3,496,107 2/1970 Lima et al ..252/499 22 Filed: Feb. 24, 1970 Appl. No.: 13,782

Int. Cl. ..C09k 3/00 Field of Search ..252/78, 75, 49.9, 49.8; 260/966 References Cited UNITED STATES PATENTS Moreton ..252/78 Primary Examiner-Leon D. Rosdol Assistant Examiner-Harris A. Pitlick At!orneyWayne C. Jaeschke, Martin Goldwasser and Daniel S. Ortiz [5 7] ABSTRACT The transmission of pressure in a closed hydraulic system is accomplished by using an effective amount-of benzylated and/or styrenated triaryl phosphate.

4 Claims, No Drawings TRANSMITTING PRESSURE IN A HYDRAULIC SYSTEM BACKGROUND OF THE INVENTION Functional fluids suitable for the operation of hydraulic mechanisms require a combination of properties which are often unattainable in many presently available materials. The properties which are required for safe and satisfactory low temperature operation include a low pour point which permits a hydraulic fluid to operate at low temperatures. Another important property which is desirable in hydraulic fluids is a flat viscosity temperature curve, that is, a high viscosity index, which allows the fluid to remain operable over a wide range of temperatures. One of the vital properties which is required for hydraulic fluids which are to be utilized in either commercial industry and mining or military use is minimum flammability. Other desirable qualities for such products include a relatively high boiling point, low corrosion characteristics and low oxidation susceptibility.

' It is known in the art that the viscosity index of hydraulic fluids normally decrease when they contain an increasing proportion of cyclic structures. (References: Murphy et al., IN- DUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 42, page 2,4 l 5; Bried et al., INDUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 45, pages 484 and reference cited therein.) Therefore, highly aromatic compounds are usually poor choices for hydraulic fluids. It is also known that benzyl compounds are normally highly susceptible to free radical attack upon the benzyl moiety by oxygen and other reactive species. Therefore, benzylated and styrenated compounds should exhibit low oxidative stability and would therefore be considered to be poor choices for hydraulic fluids.

TECHNICAL DISCLOSURE OF THE INVENTION It has now been discovered that the benzylated and styrenated triphenyl phosphates and their halogen derivatives are suitable for use as hydraulic fluids having been found, surprisingly, to possess all the above described properties required for the successful utilization of such products. It has further been discovered that the alpha-methylbenzylphenyl diaryl phosphates and their halogen derivatives are particularly suitable for such usage.

The phosphates employed in the process of the present invention are the benzylated andstyrenated triaryl phosphates having the structure:

as l. l

wherein n is a number from 0.5 to 2 inclusive, m is a number between I and 3 inclusive, x is chlorine or bromine, R, R and R are each a lower alkyl group having from one to about eight carbon atoms, a and d are each numbers from to 5 inclusive, such that the sum of a and d does not exceed 5, b is a number between 0 and 4 inclusive, c is a number from 0 to S inclusive, R and R are each hydrogen or methyl. These compounds can be prepared by the method of U.S. Pat. No. 3,428,714 or by the process described in co-pending application Ser. No. 13,780 filed Feb. 24, 1970 by Edward D. Weil.

Illustrative of these compounds are:

benzylphenyl diphenyl phosphate bis( benzylphenyl)phenyl phosphate chlorobenzylphenyl diphenyl phosphate bis(chlorobenzylphenyl)phenyl phosphate pentachlorobenzylphenyl diphenyl phosphate bis( pentachlorobenzylphenyl)phenyl phosphate pentachlorobenzylphenyl diphenyl phosphate bis( alpha-methylbenzylphenyl )phenyl phosphate bis(alpha-methylbenzylphenyl)tolyl phosphate bis( alpha-methylbenzylphenyl )xylyl phosphate bis[di( alpha-methylbenzyl )phenyl lphenyl phosphate bis[di( alpha-methylbenzyl)phenyl] tolyl phosphate bis[tri( alpha-methylbenzyl)phenyllphenyl phosphate bis[tri(alpha-methylbenzyl)phenyl]tolyl phosphate bis( alpha-methylbenzyl-4-cresyl)phenyl phosphate bis( alpha-methylbenzylphenyl )nonylphenyl phosphate bis[di(alpha-methylbenzyl)nonylphenyl lphenyl phosphate bis[tri( alpha-methylbenzyl)phenyl] nonylphenyl phosphate alpha-methylbenzylphenyl diphenyl phosphate alpha-methylbenzylphenyl ditolyl phosphate [di(alpha-methylbenzyl)phenyl] dixylyl phosphate methylchlorobenzylphenyl diphenyl phosphate bis( methylchlorobenzylphenyl )phenyl phosphate methylbromobenzylphenyl diphenyl phosphate bis( methylbromobenzylphenyl)phenyl phosphate alpha-methyl-pentachlorobenzylphenyl diphenyl phosphate bis(alpha-methyl-pentachlorobenzylphenyl)phenyl phosphate and the like, including the various isomers of the compounds.

The preferred compounds for use in the present invention are the alpha-methylbenzyl compounds, that is, those compounds having R equal to methyl and R equal to hydrogen in the generic formula given above. The use of the latter compounds is preferred-because of their high degree of oxidative stability along with their surprisingly high viscosity indices, even as compared with the other compounds coming within the scope of this invention. This is particularly surprising, since the alpha-methylbenzyl compounds would normally be expected to exhibit the lowest oxidative stability of the compounds of the present invention since the alpha-methyl group normally activates a benzyl group toward oxidative attack. Particularly, preferred compounds are:

bis( alpha-methylbenzylphenyl )phenyl phosphate alpha-methylbenzylphenyl diphenyl phosphate and their halogen substituted derivatives where the halogen is attached to the benzyl group(s).

The latter compounds are characterized by having desirable high viscosity indices. This is surprising since they have a large proportion of cyclic structures per molecule which would normally be expected to lower their viscosity indices as was stated above. Thus, one would expect the triaryl phosphates such as the tricresyl and trixylyl phosphates to have higher viscosity indices than the benzylated and styrenated triaryl phosphates of the present invention. However, the compounds of the present invention exhibit viscosity indices which are much higher than those of the triaryl phosphates.

The benzylated and styrenated triaryl phosphates used in the process of the present invention can be used individually or blended with one another, so as to obtain a fluid having properties which are intermediate between the individual phosphates thus blended. The functional fluids of this invention can also contain anticorrosion agents, defoamers and various load bearing additives all of which are well described in the literature. For economic reasons, the functional fluids of this invention can be mixed with less costly petroleum oils and/or polychloroaromatic compounds, particularly polychlorobenzyls and polychlorobiphenyls. I

The compounds used in the process of the present invention are deployed in a closed hydraulic system such as a compressor, hydraulic lift, deck edge elevators, basic oxygen furnace die casting equipment, leveling device or servo control unit in such a manner that when pressure is applied to the phosphate at a specific point within the confines of the hydraulic system, the pressure will be transmitted to any other point along the hydraulic system by the phosphate.

EXAMPLES Three compounds which are suitable for the process of the present invention were tested along with a commercially available hydraulic fluid which has a triaryl phosphate base and is sold under the name FYRQUEL 220, sold by Stauffer Chemical Chemical of New York. The results of these tests are contained in Tables 1 and 2.

From Table I it is obvious that the compounds tested are superior to the commercial product in viscosity index and aul 5 b is a number from to 4 inclusive, 0 IS a number from 0 and 5 toignition temperature.

TABLE 2 Oxidative Stability each lower alkyl having from one to about eight carbon atoms,

inclusive, a and d are each numbers from 0 and 5 inclusive,

The same samples were tested to determine their ability to resist oxidation (Federal Test Method Std. No. 791a. Method).

Fluid Alpha- Alpha-alpha- Benzylrnsthylbenzdimethylphonyl ylphenyl benzylphenyl diphenyl diphenyl diphenyl FYRQUEL phosphate phosphate phosphate 220 Viscosity at 100 F. (S.U.S.) at

0 hrs 174 367 586 212 24 hrs. 175 371 007 221 48 hrs 181 372 617 222 72 hrs 181 373 634 229 96 hrs. 189 372 654 232v Change in v 8. s 4.2 11.6 9.4 Acid number:

0 hrs 0.14 0.09 0.19 0. 24 hrs.. 0. 20 0. 0. 24 0. 92 48 hrs 0. 50 0.70 0.42 1. 96 72 hrs.. 0.80 o. 70 1.70 1.10 ilfihrs 1.40 0.90 1.89 2.10 Change in acid number 1.26 0.81 1.70 l. 90

Table 2 demonstrates that the compounds texted have an such that the sum of a and d is less than or equal to 5,' is oxidative stability comparable or superior to the commercial selected from the group consisting of chlorme'and bromine; hydraulic fluid. Further, it demonstrates that the alpha-methyl and applying pressure to said phosphate at any point in said compounds are far superior in oxidative stability and are, system so as to thereby transmit the thus applied pressure therefore, preferred. throughout said system through the medium of said The fluids employed in the present invention also perform phosphate. favorably when tested in a Vickers 104 Vane Pump. During 2. The process of claim 1, wherein R is hydrogen and R is test runs, these fluids exhibit viscosity, color and neutralizamethyl. tiun characteristics which are equal to or superior to the com- 3. A process for the transmission of pressure in a hydraulic mercially available hydraulic fluids tested. system which comprises deploying within said hydraulic What is claimed is: system an effective amount of alpha-methylbenzylphenyl l. A process for the transmission of pressure in a hydraulic diphenyl phosphate, and applying pressure to said phosphate system which comprises deploying within said hydraulic at any point in said system so as to thereby transmit the thus system an effective amount of a phosphate having structure applied pressure throughout said system through the medium corresponding to the formula: of said phosphate.

4. A process for the transmission of pressure in a hydraulic (Xh (Rm (R )o system which comprises deploying within said hydraulic R 0 s stern an effective amount of bis(al ha-meth lbenzylheny P y P -0 yl) phenyl phosphate and applying pressure to said phosphate i J lat any point in said system so as to thereby transmit the thus )a m n 3-n applied pressure throughout said system through the medium of said phosphate. wherein n is a number from 0.5 to 2 inclusive, m is a number from i to 3 inclusive, R and R are each selected from the group consisting of hydrogen and methyl, R, R and R are =7 

2. The process of claim 1, wherein R is hydrogen and R1 is methyl.
 3. A process for the transmission of pressure in a hydraulic system which comprises deploying within said hydraulic system an effective amount of alpha-methylbenzylphenyl diphenyl phosphate, and applying pressure to said phosphate at any point in said system so as to thereby transmit the thus applied pressure throughout said system through the medium of said phosphate.
 4. A process for the transmission of pressure in a hydraulic system which comprises deploying within said hydraulic system an effective amount of bis(alpha-methylbenzyl-phenyl) phenyl phosphate and applying pressure to said phosphate at any point in said system so as to thereby transmit the thus applied pressure throughout said system through the medium of said phosphate. 